OpenCV: transforming 3 channel image into 4 channel

c++, image-processing, opencv

Solution

You can convert 3 channel image to 4 channel as follows:

cv::Mat source = cv::imread(path);

cv::Mat newSrc(source.size(), CV_MAKE_TYPE(source.depth(), 4));

int from_to[] = { 0,0, 1,1, 2,2, 2,3 };

cv::mixChannels(&source,1,&newSrc,1,from_to,4);

This way channel 4 will be a duplicate of channel 3. By using a negative number in the `from_to` list, the output channel is zero filled. eg:

int from_to[] = { 0,0, 1,1, 2,2, -1,3 };

Problem

I am trying to change 3-channel image into 4-channel like this: ``` cv::VideoCapture video; video.open("sample.avi"); cv::Mat source; cv::Mat newSrc; int from_to = { 0,0, 1,1, 2,2, 3,3 }; for ( int i = 0; i < 1000; i ++ ) { video >> source; cv::mixChannels ( source, 2, newSrc, 1, from_to, 4 ); } ``` Then I got ``` too many input arguments in function call ``` for the 'mixChannels' line. Besides, I am not sure whether I am giving the arguments correctly for my goal. Can someone help me? Thank you.

Original source